Batch type vertical hot wall depressurizing CVD apparatus are widely used in film-forming processes in IC manufacturing methods for depositing silicon nitride (Si3N4), silicon oxide (SiOx) or polysilicon on wafers.
This batch type vertical hot wall depressurizing CVD apparatus contains a process tube forming a processing chamber for forming film via a thermal CVD reaction on the wafer stored inside; a boat for loading/unloading multiple wafers held in arrayed state into/from a processing chamber; a standby chamber formed directly below the process tube for maintaining the boat for loading/unloading into/from the processing chamber in standby; and a boat elevator for raising and lowering the boat and carry them in or out of the processing chamber.
In the prior art, CVD apparatus of this type are load-lock batch type vertical hot wall depressurizing CVD apparatus (hereafter called load-lock CVD apparatus) including a standby chamber formed as a vacuum container (hereafter called, load-lock type chamber) capable of withstanding pressures below atmospheric pressure. See patent document 1 and patent document 2 for examples.
The load-lock method is a method that uses a valve such as a gate valve to isolate the processing chamber from preliminary chamber (standby chamber), prevents the inflow of air into the processing chamber, and stabilize the process by reducing external disturbances such as from temperature and pressure.
Patent document 1: Japanese Patent Non-examined Publication No. 2003-151909
Patent document 2: Japanese Patent Non-examined Publication No. 09-298137